Laser processing device with tubular filter

ABSTRACT

The present invention is a laser processing device wherein adhesion of fumes to a lens can be effectively avoided. The laser processing device is provided with a laser scanner provided with protective glass on a laser output opening, and a cylindrical member having a through path through which the laser output via the protective glass passes formed on the center side in the direction of the radius. A cylindrically shaped filter is disposed on an inside wall part of the cylindrical member facing the through path. The cylindrical member discharges a gas into the through path from the filter.

TECHNICAL FIELD

This invention relates to a laser processing device with a tubularmember being interposed between a lens, which is provided at an outputopening for a laser beam, and an article to be machined.

BACKGROUND ART

In a laser processing device for performing laser welding, lasercutting, and so forth, it is necessary to prevent spatters and fumeswhich are generated from a workpiece irradiated with a laser beam, fromadhering to a lens provided at a laser output opening. The lens here isa generic name for a condensing lens, a protective glass which protectsoptics, and so forth.

In Japanese Laid-Open Patent Publication No. 01-107994, for example, alaser processing device with a substantially tubular cross-jet gasinjection unit interposed between a lens and an article to be machinedis proposed.

Specifically, the cross-jet gas injection unit has formed therein athrough path through which a laser beam passes, and a discharge pipethat discharges cross-jet gas in a direction intersecting a direction inwhich the laser beam travels and a suction pipe that draws the cross-jetgas thereinto are connected to the cross-jet gas injection unit. Byflowing the cross-jet gas in this manner, it is possible to keepspatters and fumes from reaching the lens through the through path,whereby adherence of the spatters and fumes to the lens is avoided.

SUMMARY OF INVENTION

The flow velocity of the cross-jet gas flowing near the discharge pipeand the suction pipe is, as a matter of course, higher than that ofambient air. Due to such a flow velocity difference between thecross-jet gas and ambient air, ambient air is caught up therein, whichsometimes causes a secondary air current toward the lens in the throughpath.

In this case, there is fear that the spatters and fumes carried by theabove-described air current traverse the flow of the cross-jet gas andmove to the lens side in the through path, resulting in adherence of thespatters and fumes to the lens. In particular, since the fumes areformed of metallic vapors thermally rising from a workpiece melted athigh temperatures due to laser irradiation, and the density thereof islow, the fumes easily move by being carried by the above-described aircurrent. Thus, even with the circulated cross-jet gas, it is difficultto suitably avoid the adherence of the fumes to the lens.

A main object of the present invention is to provide a laser processingdevice that can effectively avoid adherence of fumes to a lens.

An aspect of the present invention provides a laser processing deviceincluding: a laser scanner having a lens provided in an output openingfor a laser beam; and a tubular member having a through path, throughwhich the laser beam output through the lens passes, the through pathbeing formed on the center side in a radial direction thereof. In aninner wall portion, which faces the through path, of the tubular member,a tubular filter is provided, and the tubular member discharges gas fromthe filter into the through path, the through path has a cylindricalshape whose diameter is constant in an axial direction thereof, an innersurface of the filter occupies 50% or more of an inner surface of theinner wall portion, and a cross-jet gas injection unit configured toinject a cross-jet gas in a direction intersecting a traveling directionof the laser beam is provided between an irradiation target for thelaser beam and the tubular member.

In the laser processing device according to the present invention, inthe output opening for the laser beam, a condenser lens that condensesthe laser beam, a protective glass that protects optics, and so forth,are provided as the lens. The laser beam output from the laser scannerthrough this lens passes through the through path formed on the radiallycenter side of the tubular filter, which is provided in the inner wallportion of the tubular member, and is shone onto an article to beprocessed. That is, the tubular member and the filter are providedbetween the article to be processed and the lens such that the laserbeam passes through the through path.

The tubular member discharges gas into the through path through thefilter in a manner that the gas passes through the filter from an outersurface side of the filter located on the radially outward side, whichis an upstream side, toward an inner surface side thereof located on theradially center side, which is a downstream side. The velocitydifference of the gas is evened out by resistance or the like causedwhen the gas passes through the filter. Owing to this, the gas having areduced velocity difference between locations is discharged into thethrough path. As a result, between the article to be processed and thelens, a high-pressure layer in which, although the pressure thereof ishigher than that of the outside air, the occurrence of a turbulent flowis prevented, is formed. Even when such a high-pressure layer is formedin the through path, an air current that draws in fumes toward the lensbeyond the high-pressure layer is not generated. Moreover, it ispossible to generate a gentle flow of the gas directed from thehigh-pressure layer toward the article to be processed.

Therefore, with this laser processing device, since the above-describedhigh-pressure layer can be formed between the article to be processedand the lens, it is possible to prevent fumes, which are generated fromthe article to be processed, from moving across the high-pressure layertoward the lens. This makes it possible to effectively avoid theadherence of the fumes to the lens.

In the above-described laser processing device, it is preferable thatthe filter is a sintered metallic filter comprising a sintered body madeof powder of copper. Such a filter can be stably used because the filteritself can be prevented from being deteriorated even when spatters orthe like come into contact therewith. That is, by using the sinteredmetallic filter, it is possible to improve the durability of the laserprocessing device and achieve easy maintenance, for example.

In the above-described laser processing device, it is preferable thatthe filter has a cylindrical shape whose diameter is constant in anaxial direction thereof. In this case, the filter can be formed into asimple shape, which makes it possible to reduce the production cost ofthe filter and reduce the production cost of the laser processing deviceaccordingly. Moreover, since the diameter of the filter is constant inan axial direction, it is possible to effectively prevent variation invelocity of the gas, which is discharged into the through path throughthe filter, from occurring in the axial direction. This makes itpossible to form the high-pressure layer satisfactorily and avoid theadherence of the fumes to the lens.

In the above-described laser processing device, it is preferable thatthe filter is supplied with the gas via a chamber formed between thefilter and an inner surface of an outer wall portion of the tubularmember, and the gas is supplied to the chamber from a gas supply pipe ina manner that an inflow direction of the gas is oriented along at leastpart of an outer surface of the filter. In this case, the gas issupplied to the chamber so as to increase the internal pressure thereofwhile avoiding a situation in which the direction of inflow of the gasis perpendicular to the outer surface of the filter. Owing thereto, thepressure difference of the gas is evened out in the chamber, and thenthe gas is substantially evenly supplied to the whole of the filter. Asa result, it is possible to form the high-pressure layer by moreeffectively preventing variation in velocity of the gas, which isdischarged into the through path through the filter, and thus it ispossible to avoid the adherence of the fumes to the lens.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic overall side view of a laser processing deviceaccording to the present invention;

FIG. 2 is a sectional view of main portions of the laser processingdevice of FIG. 1;

FIG. 3 is a schematic perspective view of a tubular member of the laserprocessing device of FIG. 1;

FIG. 4 is a schematic plan view of the tubular member of FIG. 3; and

FIG. 5 is a schematic perspective view of a tubular member of a laserprocessing device according to another embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of a laser processing device according to thepresent invention will be described in detail with reference to theaccompanying drawings.

The laser processing device according to the present invention can besuitably used in a case where welding, cutting, boring, or the like isperformed on an article to be processed, by irradiating the same with alaser beam. In the present embodiment, as depicted in FIG. 1, an examplein which a laser processing device 10 welds flanges 14 of a set ofworkpieces 12 serving as an article to be processed, in a state wherethe flanges are placed in contact with each other, will be described.However, the embodiment is not particularly limited to this example.

The laser processing device 10 mainly includes, for example, a laserscanner 18 that is supported at the tip of an articulated robot 16, anda tubular member 22 that is detachably attached to a laser outputopening 20, which will be described later, of the laser scanner 18. Asthe articulated robot 16, it is possible to use a publicly knownarticulated robot, for example, that can move the laser scanner 18 alongthe flanges 14 of the workpieces 12 supported on a workbench 26 byclampers 24 and move the laser scanner 18 closer to or away from theworkpieces 12.

Thus, explanation of the specific configuration of the articulated robot16 will be omitted.

The laser scanner 18 has a scanner main body 28 optically connected to alaser oscillator (which is not depicted in the drawing), and, in thescanner main body 28, optical members such as a mirror 30, a condenserlens (which is not depicted in the drawing), and the like are housed.Moreover, the laser output opening 20 is provided in the scanner mainbody 28 as an opening for outputting a laser beam LB that is emittedfrom the laser oscillator and then deflected by the optical members, anda protective glass 32 (a lens) is detachably attached so as to cover thelaser output opening 20. That is, the laser scanner 18 outputs the laserbeam LB from the laser output opening 20 through the protective glass32.

As depicted in FIG. 2, the tubular member 22 has ring-shaped end faceportions (a base end face portion 34 a and a front end face portion 34b), each having an inside diameter which is substantially equal to orgreater than the size of the laser output opening 20, and a tubularouter wall portion 36 whose diameter is substantially equal to theoutside diameter of the end face portions 34 a and 34 b. It ispreferable that the end face portions 34 a, 34 b and the outer wallportion 36 are integrally formed of a relatively lightweight materialsuch as aluminum.

In the tubular member 22, a tubular inner wall portion 37 whose insidediameter is substantially equal to the inside diameter of the end faceportions 34 a, 34 b and whose diameter is smaller than the outsidediameter of the end face portions 34 a, 34 b, for example, is providedso as to be substantially coaxial with the outer wall portion 36. In theentire perimeter of this inner wall portion 37, a tubular filter 38 isprovided. It is preferable that an inner surface 38 a of the filter 38occupies 50% or more of the inner surface of the inner wall portion 37.Moreover, it is preferable that an outer surface 38 b of the filter 38occupies 50% or more of the outer surface of the inner wall portion 37.The reason therefor will be described later.

The tubular member 22 is attached near the laser output opening 20 ofthe laser scanner 18 so that a through path 39, through which the laserbeam LB output from the laser output opening 20 passes, is formed on thecenter side of the filter 38 in a radial direction. The inside diameterof the filter 38 is not limited to the above-described size and only hasto be a size that allows the laser beam LB to pass through the throughpath 39 without being interrupted by the filter 38.

Moreover, a chamber 40 is formed between an inner surface 36 a of theouter wall portion 36 and the outer surface 38 b of the filter 38 facingthe inner surface 36 a. That is, the chamber 40 is defined by the outerwall portion 36, the inner wall portion 37, and the end face portions 34a and 34 b. As depicted in FIGS. 3 and 4, gas is supplied from a gassupply source (which is not depicted in the drawing) to this chamber 40via a gas supply pipe 42 connected to the outer wall portion 36. For thepurpose of illustration, in FIGS. 1 and 2, the gas supply pipe 42 is notdepicted in the drawings. In this case, it is preferable that adirection in which the gas supply pipe 42 extends into the chamber 40 isadjusted so that an inflow direction of the gas in which the gas issupplied to the chamber 40 is oriented along at least part of the outersurface 38 b of the filter 38, in other words, the inflow direction isnot perpendicular to the outer surface 38 b. The reason therefor will bedescribed later.

In the present embodiment, as depicted in FIGS. 3 and 4, two gas supplypipes 42 are connected to the outer wall portion 36 of the tubularmember 22, and a direction in which each gas supply pipe 42 extends isadjusted so as to be inclined with respect to the radial direction ofthe filter 38. Moreover, the relationship between the directions inwhich the gas supply pipes 42 extend is set so that the gas supplied byone of the two gas supply pipes 42 and the gas supplied by the otherflow in the same direction along the circumferential direction of thechamber 40 as indicated by arrows in FIG. 4.

As the type of gas, for example, plant air or the like can be suitablyused because the plant air can be easily supplied by using a simpleconfiguration; however, the type of gas is not particularly limitedthereto. Any gas can be used, and gas can be selected from among variousgases in accordance with the material of the workpieces 12, the use ofthe laser processing device 10, and so forth.

The filter 38 is supplied with the gas via the chamber 40 from the outersurface 38 b side. In this configuration, gas passes through the filter38 from the outer surface 38 b side being an upstream side toward theinner surface 38 a side being a downstream side, and the gas is thendischarged into the through path 39. The material, thickness, pore size,and so forth, of the filter 38 may be optionally set as long as, whengas is discharged through the filter 38 into the through path 39, thefilter 38 allows the gas to flow uniformly by evening out the velocitydifference between locations due to resistance or the like caused whenthe gas passes through the filter 38.

Examples of the material of such a filter 38 include sintered metal,ceramics, and resin; however, sintered metal is preferable from thefollowing viewpoint. That is, the filter 38 (a sintered metallic filter)formed of sintered metal is a porous body which is obtained by sinteringmetal powder of copper, stainless steel, or the like. Such a filter 38can be stably used because the filter 38 itself can be prevented frombeing deteriorated even when spatters or the like come into contacttherewith. Therefore, by using the filter 38 formed of sintered metal,it is possible to improve the durability of the laser processing device10 and achieve easy maintenance, for example.

Moreover, the shape of the filter 38 is not limited to a particularshape as long as the shape is tubular; however, it is preferable thatthe filter 38 has a cylindrical shape whose diameter is constant in anaxial direction. In this case, the filter 38 can be formed into a simpleshape, which makes it possible to reduce the production cost of thefilter 38 and reduce the production cost of the laser processing device10 accordingly. Furthermore, since the diameter of the filter 38 isconstant in an axial direction, it is possible to effectively preventvariation in velocity of the gas, which is discharged into the throughpath 39 through the filter 38, from occurring in the axial direction.

In addition, concerning the filter 38, it is desirable to choose afilter having the finest possible degree of filtration accuracy in orderto achieve a laminar flow by decreasing the Reynolds number by reducinga discharge speed; in the present embodiment, a filter having thefiltration accuracy of approximately 5 μm is used.

The laser processing device 10 may include a cross-jet gas injectionunit 44 comprising a cylindrical main body 46 and as described inJapanese Laid-Open Patent Publication No. 01-107994 mentioned above, forexample, between the workpieces 12 and the tubular member 22. In thiscase, the laser beam LB that has passed through the through path 39 ofthe filter 38 further passes through the inside of cross-jet gas, andthe workpieces 12 is irradiated with the laser beam LB. That is, by adischarge pipe 48 and a suction pipe 50 which are connected to thecross-jet gas injection unit 44, the cross-jet gas is injected in adirection intersecting a direction in which the laser beam LB travels.

The laser processing device 10 according to the present embodiment isbasically constructed as described above; next, the workings and effectsthereof will be described in connection with an operation of performinglaser welding by using the laser processing device 10. In the followingdescription, a case where the laser processing device 10 includes thecross-jet gas injection unit 44 will be described.

In laser welding using the laser processing device 10, as depicted inFIG. 1, first, the laser scanner 18 is moved by the articulated robot16, and the laser output opening 20 is disposed so that the laser beamLB can be shone onto a welded portion of the workpieces 12.

Next, the laser beam LB is emitted from the above-described laseroscillator in a state in which the gas is supplied to the chamber 40 ofthe tubular member 22 from the above-described gas supply source via thegas supply pipes 42 and the cross-jet gas is made to flow between thedischarge pipe and the suction pipe of the above-described cross-jet gasinjection unit.

In the tubular member 22, as a result of the directions in which the gassupply pipes 42 extend being adjusted in the above-described manner, asdepicted in FIGS. 2 and 4, the gas is supplied to the chamber 40 whileavoiding a situation where the gas inflow direction is perpendicular tothe outer surface 38 b of the filter 38, in other words, while avoidinga situation where the gas is perpendicularly injected to the filter 38.This evens out a pressure difference in the chamber 40 and therebycauses the gas to be substantially evenly supplied to the whole of thefilter 38. As a result, it is possible to effectively prevent variationin velocity of the gas, which is discharged to the through path 39through the filter 38, and it is possible to satisfactorily form, in thethrough path 39, a high-pressure layer in which, although the pressurethereof is higher than that of the outside air, the occurrence of aturbulent flow is prevented. As depicted in FIG. 2, a gentle flow of thegas directed toward the workpieces 12 can be generated from thishigh-pressure layer.

In this way, when the tubular member 22 discharges the gas into thethrough path 39 through the filter 38, the outer surface 38 b of thefilter 38 serves as a gas suction surface and the inner surface 38 aserves as a gas discharge surface. Thus, by making the outer surface 38b of the filter 38 occupy 50% or more of the outer surface of the innerwall portion 37 as described above, the gas can be taken in from a widearea of the inner wall portion 37.

Moreover, by making the inner surface 38 a of the filter 38 occupy 50%or more of the inner surface of the inner wall portion 37, the gas whoseflow velocity has been decreased can be discharged from a wide area inhigh volume. As a result, it is possible to fill the through path 39with the gas whose pressure is slightly higher than that of ambient air,which makes it possible to prevent ambient air from being caught uptherein, and more satisfactorily form the high-pressure layer in whichthe occurrence of a turbulent flow is prevented.

Furthermore, the laser scanner 18 outputs, from the laser output opening20 through the protective glass 32, the laser beam LB guided from thelaser oscillator to the optical members in the scanner main body 28.After passing through the through path 39 of the filter 38 provided inthe tubular member 22, the laser beam LB passes through theabove-described cross-jet gas and is shone onto the welded portion ofthe workpieces 12.

In this way, by moving the scanner main body 28 along the welded portionby the articulated robot 16 while welding the spot of the workpieces 12irradiated with the laser beam LB, it is possible to perform laserwelding on the entire welded portion of the workpieces 12. At the timeof this laser welding, first, the cross-jet gas keeps spatters and fumesgenerated from the workpieces 12 from moving toward the protective glass32. In particular, the movement of the spatters, whose density is higherthan that of the fumes, can be effectively avoided by the cross-jet gas.

Moreover, even when a secondary air current is generated by flow of thecross-jet gas whose flow velocity greatly differs from that of ambientair and the fumes are caught up in the air current, the movement of thefumes toward the protective glass 32 of the through path 39 can beeffectively prevented. The reason is as follows: the above-describedhigh-pressure layer is formed between the cross-jet gas injection unitand the protective glass 32, which makes it possible to avoid the fumesfrom passing through the high-pressure layer.

That is, even when the high-pressure layer, in which the occurrence of aturbulent flow is prevented, is formed in the through path 39 asdescribed above, a secondary air current that draws the fumes into thehigh-pressure layer toward the protective glass 32 is not generated.Moreover, as depicted in FIG. 2, it is possible to guide the fumes to aside remote from the protective glass 32 by a gentle flow of the gasdirected toward the workpieces 12 from the high-pressure layer. In FIG.2, the flow of the gas is indicated by solid arrows and the flow of anair current containing the fumes is indicated by dashed arrows.

As described above, with this laser processing device 10, it is possibleto effectively avoid the adherence of spatters and fumes, which aregenerated from the workpieces 12 at the time of laser welding, to theprotective glass 32.

The present invention is not particularly limited to the above-describedembodiment, and various modifications are possible within the scope ofthe present invention.

In the laser processing device 10 according to the above-describedembodiment, the two gas supply pipes 42 are connected to the outer wallportion 36 of the tubular member 22, and a direction in which each gassupply pipe 42 extends is adjusted so as to be inclined with respect tothe radial direction of the filter 38. However, the number of gas supplypipes 42 is not limited to two, and the number of gas supply pipes 42may be one, or three or more.

Moreover, the gas supply pipes 42 may be connected to both or one of theend face portions 34 a and 34 b, in place of the outer wall portion 36of the tubular member 22. For instance, FIG. 5 shows a perspective viewof the tubular member 22 with two gas supply pipes 50 being connected tothe base end face portion 34 a. Of constituent elements in FIG. 5,constituent elements that have functions and effects which are the sameas or similar to those of the constituent elements depicted in FIGS. 1to 4 will be denoted by the same reference characters, and detailedexplanations thereof will be omitted.

In this case, as depicted in FIG. 5, it is preferable that a directionin which each gas supply pipe 50 extends is inclined with respect to theaxial direction of the tubular member 22. Moreover, it is preferablethat the relationship between the directions in which the gas supplypipes 50 extend is set so that the gas supplied by one of the two gassupply pipes 50 and the gas supplied by the other flow in the samedirection along the circumferential direction of the chamber 40. Bydoing so, it is possible to supply, to the filter 38, the gas whosevelocity distribution is made satisfactorily uniform in the chamber 40,with the inflow direction of the gas to the chamber 40 being orientedalong at least part of the outer surface 38 b of the filter 38.Therefore, it is possible to satisfactorily form a high-pressure layer,in which the occurrence of a turbulent flow is prevented, by effectivelypreventing variation in velocity of the gas discharged into the throughpath 39 through the filter 38, whereby it is possible to effectivelyprevent fumes from adhering to the protective glass 32.

Moreover, in the laser processing device 10 according to theabove-described embodiment, the chamber 40 is formed between the innersurface 36 a of the outer wall portion 36 of the tubular member 22 andthe outer surface 38 b of the filter 38 and the gas is supplied to thefilter 38 via the chamber 40. However, if the above-describedhigh-pressure layer can be formed in the through path 39, the gas may besupplied to the filter 38 without passing through the chamber 40.

Furthermore, in the laser processing device 10 according to theabove-described embodiment, the tubular member 22 is detachably attachednear the laser output opening 20 of the laser scanner 18 with theprotective glass 32. However, the tubular member 22 may be detachablyattached near the laser output opening 20 of the laser scanner 18 withno protective glass 32. In this case, it is possible to effectivelyprevent fumes and spatters from adhering to a condenser lens or thelike.

What is claim is:
 1. A laser processing device comprising: a laserscanner having a lens provided in an output opening for a laser beam;and a tubular member having a through path, through which the laser beamoutput through the lens passes, the through path being formed on acenter side in a radial direction thereof, wherein in an inner wallportion of the tubular member, which faces the through path, of thetubular member, a tubular filter is provided, the tubular memberdischarges gas from the filter toward a center side in the radialdirection of the through path, the through path has a cylindrical shapewhose diameter is constant in an axial direction thereof, an innersurface of the filter occupies 50% or more of an inner surface of theinner wall portion, the laser processing device further comprises across-jet gas injection unit, and the cross-jet gas injection unitincludes a cylindrical main body that is placed between a laserirradiation target and the tubular member and is provided with a passingpath through which the laser beam passes, a discharge tube that isconnected to the main body and discharges cross-jet gas in a directionintersecting a direction in which the laser beam travels through thepassing path, and a suction pipe that is connected to the main body anddraws the cross-jet gas, wherein the gas is supplied to a chamber formedbetween the filter and an inner surface of an outer wall portion of thetubular member from a gas supply pipe inclined with respect to a radialdirection of the filter in a manner that an inflow direction of the gasis oriented along at least part of an outer surface of the filter andthe gas flows in a circumferential direction with respect to thechamber.
 2. The laser processing device according to claim 1, whereinthe filter is a sintered metallic filter comprising a sintered body madeof copper powder.
 3. The laser processing device according to claim 1,wherein the filter has a cylindrical shape whose diameter is constant inan axial direction of the cylindrical shape.
 4. The laser processingdevice according to claim 1, wherein the filter is supplied with the gasvia the chamber.
 5. The laser processing device according to claim 1,wherein the tubular member is made of aluminum.